We all get bored sometimes. I seem to suffer from this more and more often, especially in a photographic sense. Thus, when a friend offered to loan me a thermal vision camera, I jumped at the chance to make some unique images in the spirit that the early Life photographers did using specialized cameras. This note describes a little bit about the technology, some of the problems encountered and solutions found. Hope you enjoy!

In the movie ‘Predator’, an invisible alien stalks a commando unit through the jungle. The audience is treated to a view of the world through the predator’s thermal vision eyes, which can see light in the long wave infrared (LWIR) region of 7.5 to 14 microns. Many people mistakenly think that photographic IR film and/or digital cameras converted to IR can ‘see’ heat. This is wrong, as both have very poor sensitivity above 1 micron. In order to image heat, you need a specialized device. And once you use it, you become a thermographer, rather then a photographer.

Things look very different when imaged in the LWIR region. Because the atmosphere does not scatter light at these wavelengths, skies appear very black. Human eyes show little detail due to the isothermal nature of their surface. Water absorbs LWIR like crazy and shows up like black ink on athletes. Blood circulation is also prominently displayed and resulted in some of the more unique images. I’ve called out some of these effects in the captions of figures 1a-1c.

Photo by Tom DahlinFluke Model TiR32 Thermal Imaging Camera. A view of the camera from the operator’s eye.

The camera I borrowed was a model TiR32 manufactured by the Fluke Company here in Minneapolis. Shown in figure 2, it is a rather unconventional looking device, resembling a cross between a police radar gun and a Dewalt cordless drill. I guess the industrial designers of the device recognized their customers would be maintenance personnel, not photographers. The camera has a resolution of 320 x 240 pixels, using an non-cooled focal plane array microbolometer. The f/1.0 germanium lens it comes with has a field of view of 23x17 degrees, roughly equivalent to a 80mm on a full frame DSLR. An 640x480 LCD provides an electronic viewfinder and operator interface. Images are saved to a SD card in user selectable .JPG, .PNT, or the cameras .IS2 raw file format. The later is what I used, as it allows the use of a post-processing program to adjust levels and select the output color palette used. The camera sells new for around $9000. This may seem high, but consider that imagers of much lower resolution, performance and larger size cost closer to $50,000 only a decade ago.

Most of the shots I made were at events covered over the course of a week including an indoor track meet, a swim meet plus a couple of basketball and hockey games. I shot both posed portraits and live action. Live action proved to be very difficult, as the camera is manually focused through an electronic viewfinder and is hard to use on moving subjects due to a slight time lag. The best I could do here was to pre-focus. Hockey goalies make good subjects for this as do basketball free through shooters and track athletes running in lanes. Because I was working for schools where I knew most of the athletes, it was easy to approach them after their events or games and ask for a quick portrait. This allowed me to get close enough to show circulatory detail in the skin and/or sweat/water beads, both of which made for interesting image components.

Once I was done collecting images, the fun began. Using the supplied PC based post-processing software called SmartView, I opened the camera’s .IS2 files. These contain the raw sensor data, which is essentially a grey scale image with each pixel value corresponding to temperature. Left unprocessed, the images are rather uninteresting. First, I adjusted the temperature window to suit the image. This is very similar to setting white and black levels in Photoshop. Second, I selected from contrast options. Lastly I selected a color palette to apply to the image. It is this last step that converts the grayscale image to a posterized version with the wild colors. This was done on a purely aesthetic basis where I simply played around until I found something that seemed to suit the image. A rather nice feature of SmartView is the ability to do ‘picture in picture’ images that combine the thermal image with a second visible image also taken by the camera. This is illustrated in Figure 3.

All in all, I was pretty happy with the results of the project. A two page composite (Fig 4) of the images will be run in Minnesota Score Magazine, a very cool magazine devoted to Minnesota sports. I think a similar composite of athletes at a national level track or swim meet would make for a killer Leading Off or Zoom image down the road. Who knows.

For Further Reading

Photo by Tom DahlinSwim Meet Thermal Composite – The swimmer in the left image shows warmed up muscles prior to his race. The eyes in the middle image show lack of detail because their surface temperature is even. The black background in the right image is the swimming pool

If you’re interested in learning more about alien vision, check out these resources for info on UV, IR and Thermographic imaging.

Introduction to Thermography Principles, American Technical Publishers, Fluke Corporation and The Snell Group, 2009 (This book is included by Fluke with the camera.)

Photography by Infrared, Its Principles and Applications, 3rd Edition, Henry Gibson, Wiley, New York, 1978. ISBN 0-471-15895 (Originally published in 1939, this is the definitive technical book on infrared photography.)

Kodak, "Infrared & Ultraviolet Photography", Kodak Tech. Publ. No. M-27/28-H, Eastman Kodak 1977 (Includes spectral response curves for popular Kodak IR sensitive emulsions.)Tom Dahlin is a freelance photographer based in Minneapolis, Minnesota. He covers everything from preps to the pros. His work regularly appears in Sports Illustrated, ESPN, SI-Kids and other major market sports publications. With over 25+ years of experience working as an electrical engineer in the R&D labs at 3M and Honeywell, Tom is a well qualified technology expert and enjoys using his technical skills to solve difficult imaging problems.

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